The project is designed to study cellular aging at moleculr and enzymatic level using human diploid fibroblast as model system. Experiments are designd to answer the following questtons: 1. Is the accumulation of defective enzymes in cells during aging due to changes in tRNA structure? 2. Is the accumulation of defective enzymes in cells during aging due to degeneracy of accuracy of aminoacyl tRNA synthetase? 3. Study biosynthesis of collagen by elucidation of the primary structure of alanine or proline tRNA in human diploid fibroblasts.